Hypothyroidism - Causes
Hashimoto's Thyroiditis and other Causes of Hypothyroidism
Hashimoto's thyroiditis (chronic lymphocytic thyroiditis) is a common cause of hypothyroidism (also known as an underactive thyroid). The disease was named after a Japanese physician Hakaru Hashimoto, who first described the condition in 1912. Hashimoto's thyroiditis is an autoimmune disease. The body's own immune system produces antibodies that attack and destroy the thyroid cells. There is no cure, but treatment usually involves replacing one of the thyroid hormones the thyroid no longer makes. The thyroid helps regulate body temperature, heart rate, blood pressure, body growth and metabolism (the rate at which food is turned into energy). Thyroid hormone is also part of the brain chemistry that regulates mood, cognition, appetite and behaviour. Every cell in the body needs thyroid hormone.
Autoimmune thyroid disease (Hashimoto's thyroiditis and Graves' disease) often runs in families. Other autoimmune diseases like rheumatoid arthritis, type 1 diabetes and coeliac disease can also be seen in people with a family history of autoimmune thyroid disease.
Hypothyroidism can affect you physically, mentally and emotionally. Patients with Hashimoto's tend to lose their drive, develop low self esteem and they may withdraw socially. With any thyroid imbalance patients can develop anger management problems and the women can have uncontrollable and unbearable PMT. Unfortunately the changes in personality are often very subtle, so they are not noticed by family members or friends.
The disease is diagnosed with a blood test. In Hashimoto's you will find elevated levels of antibodies, such as Thyroid Peroxidase Antibody (TPO Ab) and Thyroglobulin antibodies (Tg Ab). However 10-20 % of patients with Hashimoto's thyroiditis don't have high levels of antibodies. An ultrasound may then help confirm the diagnosis, which may show inflammation associated with autoimmune disease.
Hypothyroidism can also be caused by a lack of dietary iodine. Iodine is the raw material for the thyroid gland and is needed for the production of thyroid hormone. Iodine deficiency can result in a goitre (an inflamed thyroid gland) and causes a decrease in the production of thyroid hormone (thyroxine).
Iodine deficiency is a common cause of hypothyroidism worldwide. According to WHO (World Health Organisation) more than two billion people around the world live in areas which are prone to iodine deficiency. Australia falls within one of those areas.
Since 2009 iodized salt has been added to our bread to prevent and treat iodine deficiency disorders in Australia. However levels that are more than adequate or excessive do NOT appear to be safe, especially for people with autoimmune thyroid disease, such as Hashimoto's disease and Graves' disease. According to research an excessive amount of iodine (or more than adequate) may trigger autoimmune thyroid disease or aggravate existing thyroid disease. You need to avoid both iodine deficiency and iodine excess. Kelp supplements (see FAQ comment) are very high in iodine. If in doubt, ask your doctor for a urine test to check your iodine level.
Iatrogenic (doctor/drug induced) hypothyroidism can happen as a result of a treatment for an overactive thyroid, thyroid cancer or other medical conditions. Some drugs cause hypothyroidism too. Some examples are;
- Anti-thyroid drugs and radioactive iodine used in the treatment for an overactive thyroid
- Surgical removal of the whole thyroid gland or part of the thyroid gland to treat an overactive thyroid or thyroid cancer
- Previous radiation to head, neck or chest area
- Drugs such as interleukin-2, some anti-depressants especially lithium, some anti-psychotics, interferon, amiodarone (drug to control heart arrhythmias), barbiturates, aspirin etc. These drugs can interfere with normal thyroid hormone metabolism.
Secondary & Tertiary Hypothyroidism
Secondary hypothyroidism is not caused by the thyroid gland itself, but it can be caused by the pituitary gland or hypothalamus in the brain. The thyroid gland can become underactive if the pituitary gland fails to make enough TSH (thyroid stimulating hormone), in which case the thyroid is not being stimulated to make enough thyroid hormone. In tertiary hypothyroidism the hypothalamus does not make enough TRH (thyrotropin releasing hormone) and therefore the pituitary gland is not stimulated to make enough TSH. Both conditions can cause a low TSH and hypothyroidism (low thyroid hormone levels). Hypothyroidism cannot be diagnosed with a TSH test if either the pituitary gland or the hypothalamus is not functioning properly.
Postpartum Thyroiditis - Silent Thyroiditis
Silent thyroiditis is painless and is believed to be a silent and temporary attack on the thyroid gland by the immune system. Researchers believe that silent thyroiditis is a variation of Hashimoto's thyroiditis. It commonly occurs in the postpartum period (within the year after childbirth) and may be misdiagnosed as postpartum depression. When the thyroid cells are being destroyed more thyroid hormone leaks into the blood, producing symptoms of mild hyperthyroidism, which can last a few weeks. In some cases it can last a few months. After the attack, the thyroid gland is unable to produce enough thyroid hormone for a few weeks or longer. The thyroid gland then starts to repair itself. This condition initially may be confused with Graves' disease.
A test, called "radioactive iodine uptake count", can help you with the correct diagnosis. A high count is indicative of Graves' disease and a low count is indicative of silent thyroiditis. Antimicrosomal antibodies (thyroid antibodies) are present in at least half the patients.
Subacute Granulomatous Thyroiditis - De Quervain's Thyroiditis
Subacute granulomatous thyroiditis is caused by a viral infection. The thyroid gland becomes inflamed and very painful. Patients may experience symptoms of hyperthyroidism followed by symptoms of hypothyroidism. Most people recover completely within a few weeks or a few months. It is thought that many viruses can cause subacute thyroiditis, like the Coxsackie virus or Epstein-Barr virus. The patient may experience a fever, pain in the neck area, jaw and ears. Some blood tests may be abnormal, such as the ESR (inflammation marker) and thyroglobulin may both be elevated. The "radioactive iodine uptake count" is usually low.
Riedel's thyroiditis is also known as Riedel's struma or fibrous thyroiditis and is quite rare. This type of thyroiditis is usually painless. Normal thyroid tissue is replaced by fibrosis (formation of excess fibrous connective tissue) and it can extend to other parts of the neck.
Microbial Inflammatory Thyroiditis
This type of thyroiditis is usually caused by a Gram-positive bacterial infection, such as staphylococcus aureus or other microbes (tiny organisms). Patients with microbial inflammatory thyroiditis often have a pre-existing nodular goitre. The ESR (inflammation marker) is usually elevated. Once the infection has been identified the correct antibiotics are prescribed. If an abscess is present, then this may have to be surgically drained and occasionally a thyroid lobectomy (surgical removal of part of the thyroid gland) is necessary.
Congenital hypothyroidism (CH) describes a condition that is present at birth (congenital) and in which the thyroid gland is underactive or absent. There is usually no indication that there is anything medically wrong with these babies at the time of birth. Since the introduction of newborn screening in the 1970s, the outlook for these children changed dramatically and with early treatment they can now lead normal healthy lives. Congenital hypothyroidism occurs in approximately 1 in 3,500 babies, so each year in Australia about 70 babies are born with this condition.
Euthyroid Sick Syndrome
Euthyroid sick syndrome is also called non-thyroidal illness and can be caused by severe systemic illness, surgery or fasting. Thyroid function tests are generally abnormal in non-thyroidal illnesses. The TSH, the free T4 and the free T3 may be abnormally low and reverse T3 levels may be elevated. About 70 % of hospitalized patients have euthyroid sick syndrome. Thyroid hormone levels generally return back to normal when the patient is no longer ill. Euthyroid sick syndrome can occur in thyroid patients or patients without a history of thyroid disease. In thyroid patients who take thyroxine, the thyroid hormone levels will decrease, especially the free T3. Some doctors claim that although thyroid function tests are abnormal, the thyroid gland continues to work normally. Studies have shown however that patients can be biochemically hypothyroid and that they might benefit from thyroid hormone therapy, especially in patients who have been severely ill for a long time.
Other causes of hypothyroidism and/or possible contributing factors are;
- Genetic defects of enzymes, responsible for the manufacture of thyroid hormone
- Nutritional deficiencies, such as selenium, tyrosine, vitamin D, iron etc.
- Foods which are goitrogenic, such as unfermented soy, overconsumption of uncooked vegetables from the Brassica family (such as cabbages, broccoli, Brussels sprouts etc). ¹
- Overexposure to fluoride may reduce thyroid hormone levels. Fluoride is added to our tap water and is also used in tooth paste.
- Poor conversion from T4 to T3
- Chronic stress which results in high reverse T3 levels
- Environmental toxins such as mercury, lead, chlorine, cadmium and bromine
- Excess alcohol consumption
- Smoking (nicotine)
- Adrenal insufficiency
- Neck trauma, such as whiplash
¹ If you cook these vegetables adequately then these foods are safe to eat if eaten in moderation (cooking neutralizes goitrogens)
Copyright © 2011-2015 Monique Atkinson
Disclaimer The information provided is for educational purposes only and is not intended to be medical advice. The contents must not be relied upon in place of advice and treatment from a qualified medical practitioner. THYROID WA SUPPORT GROUP INC. and the author disclaim any liability whatsoever.